import java.util.Scanner;

/**
 * DomWon
 * Created with Intellij IDEA.
 * Description:
 * User:WEI
 * Date:2023/3/6
 * Time:8:11
 */
public class TestDome {
    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
        double avg = 0;
        double sum = 0;
        int count = 0;
        while(scan.hasNext()) {
            int i = scan.nextInt();
            if(i > 0) {
                sum += i;
                count++;
            } else {
                avg = sum / count;
                break;
            }
        }
        System.out.println(avg);
    }

    public static void main4(String[] args) {
        Scanner scan = new Scanner(System.in);
        double high = scan.nextDouble();
        int n = scan.nextInt();
        double sum = 0;
        for (int i = 1; i <= n; i++) {
            sum += high;
            if(i != 1) {
                sum += high;
            }
            high /= 2;
        }
        System.out.println(String.format("%.3f",high)+" "+String.format("%.3f",sum));
    }

    public static void main3(String[] args) {
        Scanner scan = new Scanner(System.in);
        int a = scan.nextInt();
        int b = scan.nextInt();
        System.out.println(getCM(a,b));
    }

    public static int getCM (int a,int b) {
        int tmp1 = a;
        int tmp2 = b;
        while(tmp1 % tmp2 != 0) {
            int tmp = tmp1 % tmp2;
            tmp1 = tmp2;
            tmp2 = tmp;
        }
        int ret = a * b / tmp2;
        return ret;
    }

    public static void main2(String[] args) {
        Scanner scan = new Scanner(System.in);
        int count = 0;
        while(scan.hasNext()) {
            int a = scan.nextInt();
            if(a > 0) {
                count++;
            } else {
                break;
            }
        }
        System.out.println(count);
    }

    public static void main1(String[] args) {
        long i = 0;
        long sum = 0;
        for (int j = 10; j < 10; j++) {
            i += 9 * Math.pow(10,j);
            sum += i;
        }
        System.out.println(sum);
    }
}
